The object of the present invention is a device for correcting the colour of the colour film printing machines.
There are already known in the art printing machines, the optical system of which is equipped with three different filters, which divide a condenser diaphragm hole into three segments, and the size of every filter-active field determines how to achieve three so-called basic colours in the printing machine. In previously known devices for correcting the colour there are applied bands with proper holes, which delimit every filter-active field. A disadvantage of these devices is it is very time consuming to manufacture these bands, which must be different for every negative and must contain a proper composition of three holes for every embrace of the negative. They are also known devices in which the composition of basic colours is controlled by means of easily perforated bands, carrying necessary informations in the form of small holes arranged according to a fixed code. A suitable electromechanical system sets in motion three diaphragm leaves which delimit the active section of the three different coloured bundles of light. A disadvantage of these devices is a highly developed optical system, which at first diffracts the light on three different colour bundles, and then joins and projects them onto the printed film in a suitable light combination. Another disadvantage of known devices consists in the electromechanical system working relatively slowly, because the different bundle stop-downs are achieved by discrete small steps. Another disadvantage is the currently used system of linear increases of the mechanism step change into logarithmic increases of the active section of the bundles, consisting of cams that are difficult to implement. A further shortcoming of the currently used devices is the unsatisfactory quality of the light mixture, which on the film can be recovered a structure of the light source, for example the bulb filament enabling a recovery of a structure of the light source--e.g. the bulb filament on the film. It is, therefore, an object of the present invention to create a device for correcting the colour of printing machines which would be controlled by a perforated band, but which does not require a diffraction of the light of three bundles; which, moreover, locates the diaphragm leaves in one step, which changes linear increases to logarithmic increases by means of guides having a constant radius of curvature; and the optical system of which mixes the light source perfectly. This aim is achieved by a device in which each of the three filters, dividing condenser diaphragm hole on three segments, is stopped down with two leaves, equipped with curved guides and pivoting upon fixed points, and every pair of such leaves is driven with a common lever equipped with a slide, which, during the lever turn, moves in guides of such radius of curvature, that the linear angular increase of the lever turn is accompanied by a logarithmic increase of the filter active field. The lever is driven by a multiposition electromagnetic relay, composed of magnets, the cores and armatures of which are attached to a number of two-armed rockers on a common axis; at the same time the sum of the distances between armatures and cores of a distinct pair of electromagnets is determined by an angle at which two adjoining rockers at the instant when one electromagnet of one pair is disconnected, and the second one is connected to the current source. In any successive pair of electromagnets the sum of distances between armatures and cores is half as large as the sum of an analogous previous pair. The last relay rocker is joined with the lever driven leaves, while the first rocker is joined with a screw or worm mechanism, which allows for manual introduction of additional angle setups. The device's optical system contains a glass bar functioning as a light conductor, and on the front surface of the bar is a refracted picture of the light source, while the rear surface of the bar is reproduced on the film surface by a condenser optical system.
According to the present invention, the location of the leaves--which delimit three filter-active field--in one condenser diaphragm, avoids the printing machine light from diffracting on three bundles. Owing to the suitable choice and location on the diaphragm leaves of the guide radius curvature, only circular cams are required. The use of multiposition electromagnetic relays according to the invention reduces considerably the time of diaphragm leaves transposition, because all relay rockers can be switched over at the same time. A proper choice of the distances between armatures and cores of electromagnets makes possible the relay control directly from the perforated band, coded according to the binary system of numbers.